A few:

* https://github.com/carllerche/hamcrest-rust - a (badly in need of more fleshing out) testing library * https://github.com/carllerche/nix-rust - bindings of Linux/OSX-specific APIs to Rust * https://github.com/carllerche/curl-rust - a binding of libcurl to Rust * https://github.com/carllerche/pidfile-rust - a library for using a pidfile for mutual exclusion across processes * https://github.com/carllerche/mio - a low-level IO library that attempts to implement an epoll-like interface across multiple platforms